Fitt‟s List

Allocation of Function

1. Introduction

The Technological Revolution

History:

Where did our first computers come from?

In 1822 Charles Babbage

Herman Hollerith developed the mechanical tabulator

In 1944 IBM created the Harvard Mark 1

In 1946 ENIAC was announced

Progression of technology means progression of

machines by that they are smaller, faster and more

accurate than humans can be.

What is „function allocation‟?

A classic human factor method for deciding whether a particular function will be accomplished by a person, technology (hardware or software) or some mix of person and technology

The concept of human-machine function allocation was proposed by Fitts (1951)

Used to determine if a person or a machine could better perform the function required be the system. Optimising performance makes the work done more efficient, which increases safety, quality, and ultimately profit-margins.

Allocating function, then, is the theoretical basis for delegating work to make it optimal.

Gagne (1962), Meister and Rabideau (1965), and Jordan (1963)...

What is „Fitt‟s list‟?

Fitt‟s List

Fitt‟s list is a series of statements regarding the abilities of

humans and machines, which is used to determined the

allocation of function/task assignment.

It is otherwise known as HABA-MABA.

Humans Machines

Are Are

Better Better

At At

Fitt‟s List

Humans Are Better At Machines Are Better At

Detection of nuance Operating in environments that are hostile

Perceiving a wide variety of stimuli, i.e., 5 senses Repetitive, precise operations

Pattern perception Fast response to signals

Relevant recall of information Processing information in short time periods

Creativity Performing with high accuracy

Reaction to low-probability events, i.e.,

accidents/faults

Sensitivity to stimuli beyond human sensitivity, like

infrared, etc

Flexible problem solving Multi-tasking

Utilising experience in the present Exerting large amounts of force smoothly

Performing when overloaded Insensitive to extraneous factors, such as mood, etc

Inductive reasoning/Hypothesising Deductive reasoning/Logic

So...what does it mean?

The fact that “Machines are better at operating in hostile

environments” allowed the Mars Rover to provide us with

information about Mars that humans couldn‟t ever attain.

So... What does it mean?

The fact that “Humans are better at creativity” has

allowed the product patented US D504,889 S to exist.

Or in other words...

Fitt‟s List

Utilising the theoretical framework of Fitt‟s List allows for

the designer to manufacture a product optimally:

In terms of finish;

In terms of durability;

In terms of minimum waste of resources;

In terms of time.

Ultimately, in terms of profit-margin.

Disadvantages

Disadvantages

Function allocation guidelines are often simplistic and provide only limited heuristics for allocating functions among people, hardware, and software.

Function allocation can have effects on human values. For example, automated systems may lower user satisfaction due to less human intervention.

Automated system users, may depend greatly on automation and fail to monitor the system effectively

What about dynamic allocation of functions between software and people (crash prevention systems in cars)? However when does the software allow the person to override the automation? Does the system know when someone is fatigued or when the driver is an expert?

Fitt's List is outdated, because it doesn't take into account things like hardware upgrades and that have improved exponentially since the 50's.

Difficult to apply allocation function, due to the approach requiring that some aspects are done by human operators and some by automation.

Further disadvantages

The either/or-approach might be best settled by the and-approach: humans and machines symbiotically, not humans or machines.

Over-automation, tendency of complex automation to be incomprehensible (system being too complex for the operator to control leading to automation failure).

Certain situations operators can “under-rely” on the automation, while other situations operators can “over-rely” on automation. (Parasuraman et al., 2000). This can be due to operator having insufficient knowledge about automation or when confidence is misplaced.In many cases automation replaces operator error with design error, due to lack of operational practice being incorporated into their design.

A heavy reliance on machines could lead to further socio-economic problems, such as increased unemployment, wages being lowered, work place safety diminishing, etc. (e.g. The Industrial Revolution, machines were allocated the majority of tasks in factories due to a leap in efficiency of the means of production. Jordan 1963: "to the extent that man becomes comparable to a machine we do not really need him anymore since he can be replaced by a machine.”

The List could be seen to invalid, because it makes a distinction between what we can describe and what we can‟t. machines can do a task through the form of a mathematical equation. If all tasks could

be described in terms of mathematics, then machines could do any tasks. The List, then, distinguishes what can be described mathematically and what cannot

3. Evaluation

What is evaluation ?

Last step of the function allocation process

“Measure” of the overall efficiency of the function allocation by identifying :

the task structure and its demands

the knowledge needed to perform the task

the environmental constraints

the functional and safety requirements

…

Function allocation is optimized when tasks associated with :

Technical limitations, ethics, safety…

=> allocated to humans

Human capability limits, hostile environment…

=> allocated to machines

What is evaluation ?

Sometimes, the evaluation enables to spot that the allocation

of functions was not optimal.

Re-allocation of functions.

Aspects that are evaluated

System performance

Evaluation and

re-allocation

Evaluation and

re-allocation

Aspects that are evaluated

Safety (Nina)

Aspects that are evaluated

Social impact

Evaluation and

re-allocation

Aspects that are evaluated

Usability

Evaluation and

re-allocation

Aspects that are evaluated

Cost (Nina)

Aspects that are evaluated

Job satisfaction

Performance

Satisfaction